Alkylaminoaromatic organic photoconductors

ABSTRACT

Alkylaminoaromatic compounds and vinylaminoaromatic compounds are useful as organic photoconductors in electrophotographic systems.

United States Patent 1191 Fox Oct. 23, 1973 [54] ALKYLAMINOAROMATICORGANIC 3,274,000 9/1966 Noe et a]. 96/1.5 PHOTOCONDUCTORS 3,180,7304/1965 Klupfel et al.

3,615,402 10/1971 Rule 96/1.5 [75 Inventor: Charles J. Fox, Rochester,NY. 3,627,525 12/1971 Looker et al.. 96/1.5 3,647,431 3/1972 Rossi96/1.5 Assigneez Eastman Kodak Company Looker et aL X Rochester, NY.3,290,147 12/1966 Mattor et a1. 96/1 R x 221' e "fib fi 'i'gj FOREIGNPATENTS OR APPLICATIONS I 277,494 11/1964 Netherlands 96/1 R [21] APPl-197,758 3,911,546 6/1964 Japan 96/1.5

Related U.S. Application Data 1 l gy g 'g hf h s -t 3 t PrimaryExaminerRoland E. Martin, Jr.

a an 0116 W 1C 15 a COII mua lon-m-par O Ser. No. 834,984, June 20,1969, abandoned. Ammey Robert Hampm" et [52] U.S. Cl 96/1.5, 96/1.6,260/568,

260/571, 260/573, 260/576, 260/578 ABSTRACT [51] Int. Cl 603g 5/06 I 58Field of Search 96/1 R, 1 PC, 1.5; Alkylammammam cmpunds and: 252/501matic compounds are useful as organic photoconductors inelectrophotographic systems. [56] References Cited UNITED STATES PATENTS4/1967 Mattor 96/1.5

8 Claims, 2 Drawing Figures pATgmEnnmzam' 3.767.393

/V, N D/BE/VZYLAN/L llVE PHOTOCONDUC TOI? Q) Q \l L X 4 Q LOG EXPOSURE(METER CANDLE-SECONDS) TR/PHENYLAM/NE PHO TO CONDUCTOR .1

Q Q \l L X v; E Q

LOG EXPOSURE (METER-CANDLE$ECOND$) FIG 2 CHARLES J. FOX

VENTOR.

A T TORNEY ALKYLAMINOAROMATIC ORGANIC PHOTOCONDUCTORS This is acontinuation-in-part application based on US. Ser. No. 42,441, filedJune 1, 1970, now abandoned, which is a continuation-in-part of Ser. No.834,984, filed June 20, 1969, now abandoned.

This invention relates to electrophotography, and in particular tophotoconductive compositions and elements, and to processes for theiruse.

The process of xerography, as disclosed by Carlson in US. Pat. No.2,297,691, employs an electrophotographic element comprising a supportmaterial bearing a coating of a normally insulating material whoseelectrical resistance varies with the amount of incident electromagneticradiation it receives during an imagewise exposure. The element,commonly termed a photoconductive element, is first given a uniformsurface charge, generally in the dark after a suitable period of darkadaptation. It is then exposed to a pattern of actinic radiation whichhas the effect of differentially reducing the potential of this surfacecharge in accordance with the relative energy contained in various partsof the radiation pattern. The differential surface charge orelectrostatic latent image remaining on the electrophotographicelementis then made visible by contacting the surface with a suitableelectroscopic marking material. Such marking material or toner,

whether contained in an insulating liquid or on a dry carrier, can bedeposited on the exposed surface in accordance with either the chargepattern or discharge pattern as desired. Deposited marking material canthen be either permanently fixed to the surface of the sensitive elementby known means such as heat, pressure, solvent vapor, or the like, ortransferred to a sec-' ond element to which it can similarly be fixed.Likewise, the electrostatic latent image can be transferred to a secondelement and developed there.

Various photoconductive insulating gemployed in the manufacture ofelectrophotographic elements. For example, vapors of selenium and vaporsof selenium alloys deposited on a suitable support and particles ofphotoconductive zinc oxide held in a resinous, filmforming binder havefound wide application in materials have been copying applications.

Since the introduction of electrophotography a great many organiccompounds have also been screened for their photoconductive properties.As a result, a very large number of organic compounds have been known topossess some degree of photoconductivity. Many organic compounds haverevealed a useful level of photoconduction and have been incorporatedinto photoconductive compositions.

Typical of these organic photoconductors are the triphenylamines and thetriarylmethane leuco bases. Optically clear photoconductor-containingelements having desirable electrophotographic properties can beespecially useful in electrophotography. Such electrophotographicelements can be exposed through a transparent base if desired, therebyproviding unusual flexibility'in equipment design. Such compositions,when coated as a film or layer on a suitable support, also yield anelement which is reusable; that is, it can be used to form subsequentimages after residual toner from prior images has been removed bytransfer and/or cleaning. Most of the photoconductors that have beeninvestigated thus far have been employed in films which are used inprocesses where high contrast is necessary such as in document-copyingapplications. These photoconductors and films are generally not suitablein applications requiring low contrast such as in continuous tonereproductions.

It is therefore an object of this invention to provide novelphotoconductive compositions containing a class of photoconductors whichhave low contrast characteristics.

It is a further object of the invention to provide electrophotographicelements containing novel photoconductive compositions having lowcontrast characteristics.

It is another object of this invention to provide an improvedelectrophotographic process using elements containing novelphotoconductive compositions.

These and other objects of this invention are accomplished by employingan N-alkylaminoaromatic compound or an N-vinylaminoaromatic compound asa photoconductor. Photoconductive elements containing these compoundshave good low contrast characteristics and as such, are very suitablefor use in continuous tone reproduction. In comparison, photoconductiveelements containing other photoconductors such as triarylamine arecharacterized by high contrast and are generally unsuitable forcontinuous tone reproduc-- tions.

The preferred N-alkylaminoaromatic photoconductors of this invention arecharacterized by the following formula:

1 T z Ar wherein R, can be any of the following groups:

1. an alkyl group having one to 18 carbon atoms, e.g., methyl, ethyl,propyl, butyl, isobutyl, octyl,"dodecyl, etc. including a substitutedalkyl group having aminoalkyl, e.g., diethylaminoethyl,dimethylaminopropyl, propylaminooctyl, etc., 7 g. haloaminoalkyl,e.g.,dichloroaminoethyl, N-chloro-N-ethylaminopropyl, bromoaminohexyl, etc.,

h. arylaminoalkyl, e.g., phenylaminoalkyl, diphenylaminoalkyl,N-phenyl-N- ethylaminopentyl, N-phenyl-N- chloroaminohexyl,naphthylaminomethyl,

i. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc.,

j. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyanoethyl, etc.,

k. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc.,

1. alkyl substituted with an acyl group having the formula -CR wherein Ris hydroxy, halogen, e.g., chlorine, bromine, etc., hydrogen, aryl,e.g., phenyl, naphthyl, etc., lower alkyl having one to eight carbonatoms, e.g., methyl, ethyl, propyl, etc., amino including substitutedamino, e.g., diloweralkylamino, loweralkoxy having one to eight carbonatoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy,etc.,

2. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc.,including a substituted aryl group such as a. alkoxyaryl, e.g.,ethoxyphenyl, methoxyphenyl,

propoxynaphthyl, etc.,

b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl, phenoxynaphthyl,etc.,

0. aminoaryl, e.g., aminophenyl, aminonaphthyl,

aminoanthryl, etc.,

d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl,etc.,

e. biphenylyl,

f. alkylaminoaryl, e.g., methylaminophenyl, methylaminonaphthyl, etc.and also including dialkylaminoaryl, e.g., diethylaminophenyl,dipropylaminophenyl, etc.,

g. haloaminoaryl, e.g., dichloroaminophenyl, N-

chloro-N-ethylaminophenyl, bromoaminophenyl,etc.,

h. arylaminoaryl, e.g., phenylaminophenyl, diphenylaminophenyl,N-phenyl-N- ethylaminophenyl, N-phenyl-N- chloroaminophenyl,naphthylaminophenyl, etc., i. nitroaryl, e.g., nitrophenyl,nitronaphthyl, ni-

troanthryl, etc., j. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl,

cyanoanthryl, etc., k. haloaryl, e.g., chlorophenyl, bromophenyl,chloronaphthyl, etc., I. aryl substituted with an acyl group having theformula wherein R is hydroxy, halogen, e.g., chlorine, bromine, etc.,hydrogen, aryl, e.g., phenyl, naphthyl, etc., amino includingsubstituted amino, e.g., diloweralkylamine, lower alkoxy having one toeight carbon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy,naphthoxy, etc., lower alkyl having one to eight carbon atoms, e.g.,methyl, ethyl, propyl, butyl, etc.,

m. alkaryl, e.g., tolyl, ethylphenyl, propylnaphthyl,

etc.; 3. a cycloalkyl group having four to eight carbon atoms in thecyclic nucleus, e.g., cyclobutyl, cyclohexyl, cyclopentyl, etc.,including a substituted cycloalkyl group such as a. alkoxycycloalkyl,e.g., ethoxycyclohexyl, me-

thoxycyclobutyl, propoxycyclohexyl, etc.,

b. aryloxycycloalkyl, e.g., phenoxycyclohexyl, naphthoxycyclohexyl,phenoxycyclopentyl, etc.,

0. aminocycloalkyl, e.g., aminocyclobutyl,

aminocyclohexyl, aminocyclopentyl, etc.,

d. hydroxycycloalkyl, e.g., hydroxycyclohexyl,

hydroxycyclopentyl, hydroxycyclobutyl, etc.,

e. arylcycloalkyl, e.g., phenylcyclohexyl, phenylcyclobutyl, etc.,

wherein R is hydroxy, halogen, e.g., chlorine, bromine, etc., hydrogen,aryl, e.g., phenyl, naphthyl, etc., amino including substituted amino,e.g., diloweralkylamino, loweralkoxy having one to eight carbon atoms,e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc.,loweralkyl having one to eight carbon atoms, e.g., methyl, ethyl,propyl, butyl, etc.;

4. a heterocyclic group including a substituted heterocyclic groupcontaining five to six members in the hetero nucleus and including atleast one sulfur, selenium, oxygen or nitrogen atom such as a thienylgroup, e.g., a benzothienyl group, a dibenzothienyl group, etc., apyrrolyl group, e.g., a nitropyrrolyl group, a pyrrolidinyl group, e.g.,a prolyl group, a pyrrolinyl group, a benzopyrrolyl group, e.g., anindolyl group, a carbazolyl group, a fury] group, e.g., a furfurylgroup, a benzofuryl group etc., a pyridyl group, e.g., a halopyridylgroup, an aminopyridyl group, a hydroxypyridyl group, an alkyl pyridylgroup, a nitropyridyl group, etc., a piperidyl group, a quinolyl group,an acridinyl group, a pyranyl group, a benzopyranyl group, a pyrazolylgroup, oxazolyl group, thiazolyl group, etc.

R can be any of the following groups:

1. an alkyl group having one to 18 carbon atoms, e.g., methyl, ethyl,propyl, butyl, isobutyl, octyl, dodecyl, etc., including a substitutedalkyl group having one to 18 carbon atoms such as a. alkoxyalkyl, e.g.,ethoxypropyl, methoxybutyl,

propoxymethyl, etc.,

b. aryloxyalkyl, e.g., phenoxyethyl, naphthoxymethyl, phenoxypentyl,etc.,

0. aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl, etc.,

d. hydroxyalkyl, e.g., hydroxypropyl, hydroxyoctyl,

hydroxymethyl, etc.,

e. aralkyl, e.g., benzyl, phenylethyl, etc.,

f. alkylaminoalkyl, e.g., methylaminopropyl, methylaminoethyl, etc., andalso including dialkylaminoalkyl, e.g., diethylaminoethyl,dimethylaminopropyl, propylaminooctyl, etc.,

tyl, etc.,

j. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyanoethyl, etc.,

k. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc.,

1. alkyl substituted with an acyl group having the formula wherein R ishydroxy, halogen, e.g., chorine, bromine,

etc., hydrogen, aryl, e.g., phenyl, naphthyl, etc., loweralkyl havingone to eight carbon atoms, e.g., methyl, ethyl, propyl, etc., aminoincluding substituted amino,

e.g., diloweralkylamino, lower alkoxy having one to eight carbon atoms,e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc.;

2. a cycloalkyl group having four to eight carbon atoms in the cyclicnucleus, e.g., cyclobutyl, cyclohexyl, cyclopentyl, etc., including asubstituted cycloalkyl group such as a. alkoxycycloalkyl, e.g.,ethoxycyclohexyl, me-

thoxycyclobutyl, propoxycyclohexyl, etc.,

b. aryloxycycloalkyl, e.g., phenoxycyclohexyl, 'naphthoxycyclohexyl,phenoxycyclopentyl, etc.,

0. aminocycloalkyl, e.g., aminocyclobutyl,

aminocyclohexyl, aminocyclopentyl, etc.,

d. hydroxycycloalkyl, e.g., hydroxycyclohexyl,

hydroxycyclopentyl, hydroxycyclobutyl, etc.,

e. arylcycloalkyl, e.g., phenylcyelohexyl, phenylcyclobutyl, etc.,

alkylaminocycloalkyl, e g., methylaminocyclohexyl,methylaminocyclopentyl, etc., and also including dialkylaminocycloalkyl,e.g., diethylaminocyclohexyl, dimethylaminocyclobutyl,

dipropylaminocyclooctyl, etc., I

g. haloaminocycloalkyl, e.g., dichloroaminocyclohexyl, N-chloro-N-ethylaminocyclohexyl, bromoaminocyclopentyl, etc.,

h. arylaminocycloalkyl, e.g., phenylaminocyclohexyl,diphenylaminocyclohexyl, N-phenyl-N- ethylaminocyclopentyl, N-pentyl-N-chloroaminocyclohexyl, naphthylaminocyclopentyl, etc.,.v

i. nitrocycloalkyl, e.g., nitrocyclobutyl, nitrocyclohexyl,nitrocyclopentyl, etc.,

j. cyanocycloalkyl, e.g., cyanocyclohexyl, cyanocyclobutyl,cyanocyclopentyl, etc.,

k. halocycloalkyl, e.g., chlorocyclohexyl, bromocyclopentyl,chlorocyclooctyl, etc.,

I. cycloalkyl substituted with an acyl group having the formula II C-Rwherein R is hydroxy, halogen, e.g., chlorine, bromine, etc., hydrogen,aryl, e.g.,phenyl, naphthyl, etc., amino including substituted amino,e.g., diloweralkylamino, loweralkoxy having one to eight carbon atoms,e.g.,

. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropenbutoxy, methoxy,etc., aryloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl having one toeight carbon atoms, e.g., methyl, ethyl, propyl, butyl, etc.;

3. a vinyl group including a substituted vinyl group such as a.alkoxyvinyl, e.g., ethoxyvinyl, methoxyvinyl,

propoxyvinyl, etc.,

b. aryloxyvinyl, e.g., phenoxyvinyl, naphthoxyvinyl,

etc.,

0. arylvinyl, e.g., styryl, naphthylvinyl, etc.,

d. alkylvinyl, e.g., propenyl, butenyl, etc.;

Ar represents an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl,etc., including a substituted aryl group such as a. alkoxyaryl, e.g.,ethoxyphenyl, methoxyphenyl,

propoxynaphthyl, etc.,

b. alkoxyaryl, e.g., ethoxyphenyl, naphthoxyphenyl, phenoxynaphthyl,etc.,

0. aminoaryl, e,g., aminophenyl, aminonaphthyl,

aminoanthryl, etc.,

d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl,etc.,

e. biphenylyl,

f. alkylaminoaryl, e.g., methylaminophenyl, me-

thylaminonaphthyl, etc., and also including dialkylaminoaryl, e.g.,diethylaminophenyl, dipropylaminophenyl, etc.,

g. haloaminoaryl, e.g., dichloroaminophenyl, N-

chloro-N-ethylaminophenyl, bromoaminophenyl, etc., h. arylaminoaryl,e.g., phenylaminophenyl, diphenylaminophenyl, N-phenyl,N-ethylaminophenyl, N-phenyl, N-

ronaphthyl, etc., I. aryl substituted with an acyl group having theformula Ma II C-R wherein R is hydroxy, halogen, e.g., chlorine,bromine, etc., hydrogen, aryl, e.g., phenyl, naphthyl, etc., aminoincluding substituted amino, e.g., diloweralkylamino, lower alkoxyhaving one to eight carbon atoms, e.g., butoxy, methoxy, etc., aryloxy,e.g., phenoxy, naphthoxy, etc., loweralkyl having one to eight carbonatoms, e.g., methyl, ethyl, propyl, butyl, etc., m. alkaryl, e.g.,tolyl, ethylphenyl, propylnaphthyl,

etc. In the above formula at least one of R and R is preferably eitheran alkyl group, a vinyl group, or a cycloalkyl group.

Typical compounds which belong to the herein described general class ofphotoconductive materials include the following compounds listed inTable I below.

TABLE I Photoconductor Chemical Name I N,N-Dibenzylaniline llN-Benzyl-N-phenylaniline Ill N,N-Bis(cyclohexylmethyl)aniline lVN,N-Bis(cyclohexylethyl)aniline V N ,N-Diphenethylaniline VIN,N-Diethylaniline 7 VII l-Dimethylaminonaphthalene Vllll-Diethylaminonaphthalene IX .N-E -sb sx ssi ins. XN-EHHYlN-4-n-octylphenyl-4-noctyaniline XI N,N-Diethyl-N,N'-

diphenylethylenediamine X11 hwyc shsxylr irshss ssifiss XIIIN-Ethyl-l-J-(2-phenoxyethyl)-3 methylaniline XIV l-Dimethylaminofluorenexv N-Benzyl-N-(4-pyridyl)aniline XVI N-Benzyl-N-(4-quinolyl)aniline XVIIN-Styryl-N-phenylaniline The advantages attributable to the use of thephotoconductive materials described herein are further explained withreference to the drawings. The various configurations set forth in thedrawings are not to scale and are included only for a betterunderstanding of the invention. FIG. 1 is a plot of density (equal tothe log of the reciprocal of the transmittance (T)) versus log exposureand the resultant S shaped curve obtained is known as either an H and Dcurve or characteristic curve for a photoconductive element containingN,N- dibenzylaniline as the photoconductor and Lexan 145 (apolycarbonate resin sold by General Electric Co.) as the binder, thephotoconductor being 25 percent by weight of the photoconductivecomposition. This curve shows the relationship between increasingexposure and the increased density of the developed image. The curve isprepared by exposing a charged element containing one of thephotoconductors described herein to a light source of given intensitythrough a 0.15 log E increment step tablet having 21 steps. After theexposure is completed, the resultant latent image on the surface of thephotoconductive element is developed with an electrostatic toner in amanner to produce a reversal image. A densitometer is then used tomeasure the density of each of the developed steps. An analysis of thecurve in FIG. I indicates that the film is responsive to small exposuresas well as relatively larger exposures. The slope of the intermediateportion of the curve, 7, is such that intermediate tones are reproducedindicating that the film has a broad exposure range. An unexpectedproperty of the photoconductors described herein is the relatively low'y of the H and D curve.

For purposes of comparison, FIG. II represents the H and D curve of thecharacteristic curve for a photoconductive element containing a highcontrast material such as a photoconductive composition containing atriphenylamine photoconductor and Lexan 145 as the binder, thephotoconductor being 25 percent by weight of the photoconductivecomposition. An inspection of this curve reveals that the intermediatestraight line portion of the curve has a very steep slope (i.e., high7). The difference in exposure required to produce images having verylow density and very high density is small. Thus, there is little or noopportunity for the reproduction of intermediate tones and the resultantimage is generally either black or white. Materials having such highcontrast characteristics are unsuitable for continuous tonereproductions.

Electrophotographic elements of the invention can be prepared with thephotoconducting compounds of the invention in the usual manner, i.e., byblending a dispersion or solution of a photoconductive compound togetherwith a binder, when necessary or desirable, and coating or forming aself-supporting layer with the photoconductor-containingmaterial.Mixtures of the photoconductors described herein can be employed.

Likewise, other photoconductors known in the art can be combined withthe present photoconductors. In addition, supplemental materials usefulfor changing the spectral sensitivity or electrophotosensitivity of theelement can be added to the composition of the element when it isdesirable to produce the characteristic effect of such materials.

The photoconductive layers of the invention can also be sensitized bythe addition of effective amounts of sensitizing compounds to exhibitimproved electrophotosensitivity. Sensitizing compounds useful with thephotoconductive compounds of the present invention can be selected froma wide variety of materials, including such materials as pyrylium dyesalts including thiapyrylium dye salts and selenapyrylium dye saltsdisclosed in VanAllan et al. U.S. Pat. No. 3,250,615; fluorenes, such as7,12-dioxo-l3-dibenzo(a,lij fluorene: 5 ,10-dioxo-4a,ll-diazabenzo(b)fluorene, 3 ,1 3-dioxo- 7-oxadibenzo(b,g)fluorene, andthe like; aromatic nitro compounds of the kinds described in U.S. Pat.No. 2,610,120; anthrones like those disclosed in U.S. Pat. No.2,670,284; quinones, U.S. Pat. No. 2,670,286;

benzophenones U.S. Pat. No. 2,670,287; thiazoles U.S.

Pat. No. 2,732,301; mineral acids; carboxylic acids, such as maleicacid, dichloroacetic acid, and salicyclic acid; sulfonic and phosphoricacids; and various dyes, such as cyanine (including carbocyanine),merocyanine, diarylmethane, thiazine, azine, oxazine, xanthene,phthalein, acridine, azo, anthraquinone dyes and the like and mixturesthereof. The sensitizers preferred for use with the compounds of thisinvention are selected from pyrylium salts including selenapyryliumsalts and thiapyrylium salts, and cyanine dyes including carbocyaninedyes.

Where a sensitizing compound is employed with the binder and organicphotoconductor to form a sensitized electrophotographic element, it isthe normal practice to mix a suitable amount of the sensitizing compoundwith the coating composition so that, after thorough mixing, thesensitizing compound is uniformly distributed in the coated element.Other methods of incorporating the sensitizer or the effect of thesensitizer may, however, be employed consistent with the practice ofthis invention. In preparing the photoconductive layers, no sensitizingcompound is required to give photoconductivity in the layers whichcontain the photoconducting substances, therefore, no sensitizer isrequired in a particular photoconductive layer. However, sincerelatively minor amounts of sensitizing compound give substantialimprovement in speed in such layers, the use of a sensitizer ispreferred. The amount of sensitizer that can be added to aphotoconductor-incorporating layer to give effective increases in speedcan vary widely. The optimum concentration in any given case will varywith the specific photoconductor and sensitizing compound used. Ingeneral, substantial speed gains can be obtained where an appropriatesensitizer is added in a concentration range from about 0.0001 to about30 percent by weight based on the weight of the film-forming coatingcomposition. Normally, a sensitizer is added to the coating compositionin an amount by weight from about 0.005 to about 5.0 percent by weightof the total coating composition.

Preferred binders for use in preparing the present photoconductivelayers are film-forming, hydrophobic polymeric binders having fairlyhigh dielectric strength which are good electrically insulating,film-forming vehicles. Materials of this type comprise styrenebutadienecopolymers; silicone resins; styrene-alkyd resins; silicone-alkydresins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidenechloride); vinylidene chloride-acrylonitrile copolymers; poly(vinylacetate); vinyl acetate-vinyl chloride copolymers; poly( vinyl acetals),such as poly(vinyl butyral); polyacrylic and methacrylic esters, such aspoly(methylmethacrylate), poly(n-butylmethacrylate), poly(isobutylmethacrylate), etc.; polystyrene; nitrated polystyrene;polymethylstyrene; isobutylene polymers; polyesters, such aspoly(ethylenealkaryloxyalkylene terephthalate); phenolformaldehyderesins; ketone resins; polyamides; polycarbonate; polythiocarbonates;poly(ethyleneglycolco-bishydroxyethoxyphenyl propane terephthalate);copolymers of vinyl haloarylates and vinyl acetate such aspoly(vinyl-m-bromobenzoate-covinylacetate); etc. Methods of makingresins of this type have been described in the prior art, for example,styrene-alkyd resins can be prepared according to the method describedin US. Pat. Nos. 2,361,019 and 2,258,423. Suitable resins of the typecontemplated for use in the photoconductive layers of the invention aresold under such tradenames as Vite] PE-lOl, Cymac, Piccopale 100, SaranF-220, Lexan 105 and Lexan 145. Other types of binders which can be usedin the photoconductive lay- 1 ers of the invention include suchmaterials asparaffin,

mineral waxes, etc.

Solvents useful for preparing coating compositions with thephotoconductors of the present invention can include a wide variety oforganic solvents for the components of the coating composition. Forexample, benzene; toluene; acetone; 2-butan0ne; chlorinated hydrocarbonssuch as methylene chloride; ethylene chloride; and the like; ethers,such as tetrahydrofuran and the like, or mixtures of such solvents canadvantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the photoconductorsdisclosed herein useful results are obtained where the photoconductivesubstance is present in an amount equal to at least about 1 weightpercent of the coating composition. The upper limit in the amount ofphotoconductive material present can be widely varied in accordance withusual practice. It is normally required that the photoconductivematerial be present in an amount ranging from about 1 weight percent ofthe coating composition to about 99 weight percent of the coatingcomposition. A preferred weight range for the photoconductive materialin the coating composition is from about weight percent to about 60weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. Normally, a wet coating thickness in the range of about0.001 inch to about 0.01 inch is useful in the practice of theinvention. A preferred range of coating thickness is from about 0.002inch to about 0.006 inch before drying although such thicknesses canvary widely depending on the particular application desired for theelectrophotographic element.

Suitable supporting materials for coating the photoconductive layers ofthe present invention can include any of the electrically conductingsupports, for example, paper (at a relative humidity above percent);aluminum-paper laminates; metal foils, such as aluminum foil, zinc foil,etc.; metal plates, such as aluminum,

copper, zinc, brass, and galvanized plates; vapor deposited metal layerssuch as silver, nickel or aluminum on conventional film supports such ascellulose acetate, poly(ethylene terephthalate), polystyrene and thelike conducting supports.

An especially useful conducting support can be prepared by coating atransparent film support material such as poly(ethylene terephthalate)with a layer containing a semiconductor dispersed in a resin. A suitableconducting coating can be prepared from the sodium salt of acarboxyester lactone of the maleic anhydridevinyl acetate copolymer,cuprous iodide and the like. Such conducting layers and methods fortheir optimum preparation and use are disclosed in US. Pat. Nos.3,007,901, 3,245,833 and 3,267,807.

The compositions of the present invention can be employed inphotoconductive elements useful in any of the wellknownelectrophotographic processes which require photoconductive layers. Onesuch process is the xerographic process. In a process of this type, anelectrophotographic element held in the dark, is given a blanketelectrostatic charge by placing it under a corona discharge to give auniform charge to the surface of the photoconductive layer. This chargeis retained by the layer owing to the substantial dark insulatingproperty of the layer, i.e., the lower conductivity of the layer in thedark. The electrostatic charge formed on the surface of thephotoconductive layer is then selectively dissipated from the surface ofthe layer by imagewise exposure to light by means of a conventionalexposure operation such as for example, by a contactprinting technique,or by lens projection of an image, or reflex or bireflex techniques andthe like, to thereby form a latent electrostatic image in thephotoconductive layer. Exposing the surface in this manner forms apattern of electrostatic charge by virtue of the fact that light energystriking the photoconductor causes the electrostatic charge in the lightstruck areas to be conducted away from the surface in proportion to theintensity of the illumination in a particular area.

The charge pattern produced by exposure is then de- I veloped ortransferred to another surface and developed there, i.e., either thecharge or uncharged areas rendered visible, by treatment with a mediumcomprising electrostatically responsive particles having opticaldensity.The developing electrostatically responsive particles can be in the formof a dust, or powder and generally comprise a pigment in a resinouscarrier called a toner. A preferred method of applying such a toner to alatent electrostatic image for solid area development is by the use of amagnetic brush. Methods of forming and using a magnetic brush tonerapplicator are described in the following US. Pat. Nos.: 2,786,439;2,786,440; 2,786,441; 2,811,465; 2,874,063; 2,984,163; 3,040,704;3,117,884; and reissue Re 25,779. Liquid development of the latentelectrostatic image may also be used. In liquid development thedeveloping particles are carried to the imagebearing surface in anelectrically insulating liquid carrier. Methods of development of thistype are widely known and have been described in the patent literature,for example, US. Pat. No. 2,297,691 and in Aus-' tralian Pat. No.212,315. In dry developing processes the most widely used method ofobtaining a permanent record is achieved by selecting a developingparticle which has as one of its components a low-melting resin. Heatingthe powder image then causes the resin to melt or fuse into or on theelement. The powder is, therefore, caused to adhere permanently to thesurface of the photoconductive layer. In other cases, a transfer of thecharge image or powder image formed on the photoconductive layer can bemade to a second support such as paper which would then become the finalprint after developing and fusing or fusing respectively. Techniques ofthe type indicated are well known in the art and have been described ina number of US. and foreign patents, such as U.S. Pat. Nos. 2,297,691and 2,551,582, and in RCA Review, vol. 15 (1954) pages 469-484.

The compositions of the present invention can be used inelectrophotographic elements having many structural variations. Forexample, the photoconductive composition can be coated in the form ofsingle layers or multiple layers on a suitable opaque or transparentconducting support. Likewise, the layers can be contiguous or spacedhaving layers of insulating material or other photoconductive materialbetween layers or overcoated or interposed between the photoconductivelayer or sensitizing layer and the conducting layer. It is also possibleto adjust the position of the support and the conducting layer byplacing a photoconductor layer over a support and coating the exposedface of the support or the exposed or overcoated face of thephotoconductor with a conducting layer. Configurations differing fromthose contained in the examples can be useful or even preferred for thesame or different application for the electrophotographic element.

The following examples are included for a further understanding of thisinvention.

Example 1 A composition in the form of a dope consisting of Organicphotoconductor.3 l g Polymeric bluegrass"ib 'aiiiiyaarsaaaiasin sold byGeneral Electric Co.)-.94 g Sensitizer(2,4-bis(4-ethoxyphenyl)-6-(4-amyloxystyryl) pyrylium fluoroborate.0l25 g Methylene chloride--l0.00 gis coated at a wet thickness of 0.004 inch on an aluminum surface toprovide the coatings described in Table II. In a darkened room, thesurface of the photoconductive layer, so prepared, is charged to apotential 'of about +600 volts under a corona charger. The layer is thencovered with a transparent sheet bearing a pattern of opaque andlight-transmitting areas and exposed to the radiation from anincandescent lamp with an illumination intensity of about 75meter-candles for 12 seconds. The resulting electrostatic latent imageis developed by cascading over the surface of the layer a mixture ofnegatively charged thermoplastic toner particles and glass beads. A goodreproduction is obtained in each instance.

TABLE II Photoconductor Image Reproduced None present No I N,N-Dibenzylaniline Yes ll N-Benzyl-N-phenylaniline Yes IllN,N-Bis(cyclohexylmethyl) aniline Yes 1V N,N-Bis(cyclohexylethyl)aniline Yes Example 2 Coatings containing 25% of an N,N-dialkylanilinein 6 Lexan and sensitized with 1%2,4-bis(4-ethylphenyl)-6-(4-styrylstyyl)pyrylium perchlorate areprepared and examined by the procedure in Example 1. The results arelisted in Table III.

TABLE III Photoconductor Image Reproduced I N,N-Dibenzylaniline Yes IIN,N-Diphenethylaniline Yes III N,N-Bis(cyclohexylmethyl) aniline Yes IVN,N-Bis(cyclohexylethyl) aniline Yes None present No Example 3 Coatingscontaining 20% of N ,N-diethylanilin e yr in Lexan 105 and sensitizedwith 1% 2,4-bis(4-ethyl phenyl)-6-(4-styrylstyryl)pyrylium perchlorateare prepared and examined according to the procedure2,4,7-trinitrofluorenone sensitizer are prepar e c lby the method inExample 1 from a dope consisting of 0.15 gPhotoconductor 0.50 gVitel l0la polyester resin sold by Goodyear Tire & Rubber Co. comprising essentially poly)4,4-isopropylidenebisphenoxyethyl-co-ethyleneterephthalate) 0.002 gSensitizer 5 mlDichloromethane and examinedaccording to the procedure set forth in Example 1. A good reproductionis obtained. When the photoconductor is omitted, no image is reproduced.xample 5.

Coatings containing 25 of N-ethyl-N-4-n-octyl phenyl-4-n-octylaniline(X) in polystyrene binder with 1% of2,6-bis(4-ethylphenyl)-6-(4-pentyloxy phenyl)-thiapyrylium perchloratesensitizer are prepared as described in Example 1 and the speeds aremeasured by exposure through a 0.15 log E step wedge and development ofthe resulting latent image with a positive fringe toner. The number ofvisible steps developed is l4. When the aniline compound is omitted, nocomplete visible steps are obtained.

Example 6 Coatings containing 25% of N,N'-diethyl-N,N'-dishs l n d smi s(X in VitsllQLbinde with 1%2,6-bis(4-ethylphenyl)-6-(4-pentyloxyphenyl)- thiapyrylium perchloratesensitizer are prepared and evaluated as described in Example 5. Thenumber of visible steps developed is 18, when the aniline is omittedonly ten visible steps are reproduced.

Example 7 Coatings containing 20% of N-cyclohexyl-N- phenylaniline (XII)photoconductor in Vitel 101391 ester with 0.8%2,6-bis(4-ethylphenyl)-4-(4-pentyloxy- I phenyl)thiapyrylium perchlorateare prepared and tested by the method in Example 1 from a dopeconsisting of 0.25 gPhotoconductor 1.00 gVitel 101 0.01 gSensitizer 9.6g- Dichloromethane ethyl-N-phenylaniline (IX) orN-ethyl-N-(Z-phenoxyethyl)-3methylaniline in Lexan 105 and sensitizedwith 1% 2,6-bis(4-ethoxyphenyl)-4-(4-pentyloxyphenyl)thiapyryliumperchlorate are prepared and examined by the procedure in Example 1. Theresults are listed in Table IV.

TABLE IV v 20% Photoconductor in Legal] 1( 5 vvi th 1 sensitize;

Image Reproduced IX N-Ethyl-N-phenylaniline Yes XlVN-Ethyl-n-(2-phenoxyethyl)-3- methylsniline Yes None present N0 Example10 Several compositions are prepared comprising Vitel 101 polyesterbinder, by weight photoconductor and 0.8% by weight of the sensitizer2,6-bis(4-ethylphenyl)-4-(4-n-amyloxyphenyl)thiapyrylium perchlorate alldissolved in methylene chloride. The' resultant dopes are coated as inExample 1 to form elements 1 through 6 each of which is charged under anegative corona and imagewise exposed to a 3,000 K tungsten sourcethrough a neutral density gray scale. The exposure causes reduction ofthe surface potential of the el-' ement under each step of the grayscale from its initial potential, V,,, to some lower potential, V, whoseexact value depends upon the actual amount of exposure inmeter-candle-seconds received by the area. The results of thesemeasurements are then plotted on a graph of surface potential V vs. logexposure for each step. The actual speed of the photoconductivecomposition can then be expressed in terms of the reciprocal of theexposure required to reduce the surface potential to any fixed, selectedvalue. Herein, unless otherwise stated, the actual negative speed is thenumerical expression of l04fdivided by the exposure inmeter-candle-seconds required to reduce the initially charged surfacepotential V, to a value 100 volts lower (shoulder speed) and to anabsolute value of 100 volts (toe speed). In addition, the contrast isdetermined as the tangent of the angle made by extending the straightline portion of the electrical speed curve in mid-scale to the baseaxis. The results of these measurements using diflerent photoconductorsof the prior art (elements 2 through 6) are shown below.

Element Speed Cons2!9 QL QtQr u mm. gs i l 19g 1 N ,N-Dibenzylaniline220/ 3.0 1.04 2 Di-Z-naphthylamine 50/0 1.23 3 N-Phenyl-Z-naphthylamfine36/0 1.04 4 N-Phenyl-l-naphthylamine 32/0 1.07 5 Diphenylamine 6 2,5-Bis(p-diethylamino phenyl)-l ,3 ,4-oxadiazole 63/4.0 1.66

Speed too low to obtain a meaningful sensitometric curve.

obtained with a photoconductor of the present invention. Whereas, priorconductors have low or no speed and/or high contrast.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. A photoconductive composition comprising a polymeric film-formingbinder, an organic photoconductor and a sensitizing amount of asensitizer for said photoconductor, said photoconductor having theformula:

... Wig; .1

Ar wherein:

R is selected from the group consisting of an alkyl group having up to18 carbon atoms, a phenyl group, a naphthyl group, an anthryl group, afluorenyl group and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus;

R is selected from the group consisting of an alkyl group having up to18 carbon atoms and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus; and

Ar is selected from the group consisting of phenyl,

naphthyl,anthry] and fluorenyl.

2. An electrophotographic element comprising a conductive support havingthereon a photoconductive composition comprising a polymericfilm-forming binder, an organic photoconductor and a sensitizing amountof a sensitizer for the photoconductor, said photoconductor having theformula:

R,NR 1. wherein:

R is selected from the group consisting of an alkyl group having up to18 carbon atoms, a phenyl group, a naphthyl group, an anthryl group, afluorenyl group and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus;

R is selected from the group consisting of an alkyl group having up to18 carbon atoms and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus; and

1 Ar is selected from the group consisting of phenyl,

naphthyl, anthryl and fluorenyl.

3. In an electrophotographic process for forming low I contrast imageswherein an electrostatic charge pattern is formed on anelectrophotographic element which comprises a conductive support havingthereon a photoconductive layer comprising a polymeric filmformingbinder, an organic photoconductor and a sensitizer for saidphotoconductor, the improvement wherein'said photoconductor has theformula:

"" RFfIT EI wherein:

R is selected from the group consisting of an alkyl group having up to18 carbon atoms, a phenyl group, a naphthyl group, an anthryl group, afluorenyl group and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus;

R is selected from the group consisting of an alkyl group having up to18 carbon atoms and a cycloalkyl group having four to eight carbon atomsin the cyclic nucleus; and

Ar is selected from the group consisting of phenyl,

naphthyl, anthryl and fluorenyl.

4. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a. from about 10 toabout 60 percent by weight based on said photoconductive composition ofN,N- dibenzylaniline as a photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005%to about by weight based on said photoconductive composition of asensitizer for said photoconductive composition.

5. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a. from about to about60 percent by weight based on said photoconductive composition ofN-benzyl- N-phenylaniline as a photoconductor,

b. a film-formin g polymeric binder for said photoconductor and c.0.005% to about 5% by Weight based on said photoconductive compositionof a sensitizer for said photo-conductive composition.

6. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a. from about 10 toabout 60 percent by weight based on said photoconductive composition ofN ,N- bis(cyclohexylmethyl)aniline as a photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005%to about 5% by weight based on said photoconductive composition of asensitizer for said photoconductive composition.

7. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a. from about 10 toabout 60 percent by weight based on said photoconductive composition ofN,N- bis(cyc1ohexylethyl)aniline as a photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005%to about 5% by weight based on said photoconductive composition of asensitizer for said photoconductive composition.

8. An electrophotographic element comprising a support having coatedthereon a photoconductive composition comprising a. from about 10 toabout 60 percent by weight based on said photoconductive composition ofN,N- diphenethylaniline as a photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. 0.005%to about 5% by weight based on said photoconductive composition of asensitizer for said photoconductive composition.

2. An electrophotographic element comprising a conductive support havingthereon a photoconductive composition comprising a polymericfilm-forming binder, an organic photoconductor and a sensitizing amountof a sensitizer for the photoconductor, said photoconductor having theformula:
 3. In an electrophotographic process for forming low contrastimages wherein an electrostatic charge pattern is formed on anelectrophotographic element which comprises a conductive support havingthereon a photoconductive layer comprising a polymeric film-formingbinder, an organic photoconductor and a sensitizer for saidphotoconductor, the improvement wherein said photoconductor has theformula:
 4. An electrophotographic element comprising a support havingcoated thereon a photoconductive composition comprising a. from about 10to about 60 percent by weight based on said photoconductive compositionof N,N-dibenzylaniline as a photoconductor, b. a film-forming polymericbinder for said photoconductor and c. 0.005% to about 5% by weight basedon said photoconductive composition of a sensitizer for saidphotoconductive composition.
 5. An electrophotographic elementcomprising a support having coated thereon a photoconductive compositioncomprising a. from about 10 to about 60 percent by weight based on saidphotoconductive composition of N-benzyl-N-phenylaniline as aphotoconductor, b. a film-forming polymeric binder for saidphotoconductor and c. 0.005% to about 5% by weight based on saidphotoconductive composition of a sensitizer for said photo-conductivecomposition.
 6. An electrophotographic element comprising a supporthaving coated thereon a photoconductive composition comprising a. fromabout 10 to about 60 percent by weight based on said photoconductivecomposition of N,N-bis(cyclohexylmethyl)aniline as a photoconductor, b.a film-forming polymeric binder for said photoconductor and c. 0.005% toabout 5% by weight based on said photoconductive composition of asensitizer for said photoconductive composition.
 7. Anelectrophotographic element comprising a support having coated thereon aphotoconductive composition comprising a. from about 10 to about 60percent by weight based on said photoconductive composition ofN,N-bis(cyclohexylethyl)aniline as a photoconductor, b. a film-formingpolymeric binder for said photoconductor and c. 0.005% to about 5% byweight based on said photoconductive composition of a sensitizer forsaid photoconductive composition.
 8. An electrophotographic elementcomprising a support having coated thereon a photoconductive compositioncomprising a. from about 10 to about 60 percent by weight based on saidphotoconductive composition of N,N-diphenethylaniline as aphotoconductor, b. a film-forming polymeric binder for saidphotoconductor and c. 0.005% to about 5% by weight based on saidphotoconductive composition of a sensitizer for said photoconductivecomposition.